The invention relates to a device of a camera for image acquisition. The device comprises a sensor chip which has an optically active surface, referred to hereafter as the imager surface, and which is situated on a carrier either directly or indirectly by interposing a circuit board. The sensor chip has contact pads, via which the sensor chip is electrically connected to the circuit board. An objective for imaging the environment on the sensor chip is assigned to the sensor chip, the objective being retained in an objective carrier and being oriented in its situation and inclination in relation to the imager surface.
Cameras of this type are employed for various applications in order to optically capture the environment, process and analyze it, and employ the data thus obtained to control devices or methods, for example, or also to control the camera itself.
The construction of such a camera typically comprises at least one electronic sensor chip, to which an objective, which is adapted to the particular application and also the resolution of the sensor and the size of the imager surface, is assigned. The sensor chip is mounted on a circuit board on which signal lines, supply lines, and possibly at least signal preprocessing units are situated.
The circuit board, including the described superstructures, is mounted on a carrier. The objective is situated above each sensor chip at the spacing required in accordance with the optical system of the objective. It is installed on carrier and circuit board in such a way that the sensor chip is completely enveloped and light is only incident on the sensor chip through the lenses. The objective has a separate housing for this purpose if needed.
The carrier and also its connections to the circuit board and to the objective or its housing must fulfill different mechanical, thermal, chemical, and electrical requirements for the various applications, the mechanical stability particularly being ensured for use in mobile devices. The carriers are usually manufactured from metal for this reason. The camera is connected to external devices, which may be used for, e.g., the movement of the camera via the carrier so that a plane of the carrier is defined as a reference surface, to which the sensor chip and the objective are oriented, for the orientation of the camera in relation to these external devices.
An exact orientation of sensor chip and objective to one another is an essential condition for an analyzable image quality. This orientation comprises the lateral orientation of both components on the one hand, via which in particular the image quality in the boundary area of the imager surface and thus the dimension of the imager surface providing analyzable results are determined. The orientation also comprises the inclination of both components to one another, which may be established via the inclination of each individual component to the same reference surface. The inclination of the imager surface alone to the reference surface also has an influence on the recorded image and its analysis, because a movement or positioning of the camera and thus the imager surface occurs in relation to the reference surface, as described above.
If the imager surface and reference surface are tilted to one another, the recorded image is a function of a rotation of the camera around its optical axis. This effect is known as “tilt” or “yaw, pitch, and roll,” and may only be avoided by an exact and very complex parallel orientation of the imager surface to the reference surface. This orientation is accordingly also to be produced in the same precision for the inclination of the objective to the reference surface and is particularly to be maintained independently of thermal and mechanical strains during the entire service life of the camera. This often proves to be difficult because of the differing spatial expansions of the sensor chip and objective carrier.
Furthermore, losses in image quality may arise due to a shift of the sensor chip and the objective in relation to one another, for example. On the other hand, the impairments are also possible due to scattered light, which is incident on the sensor chip through defective connections between the carrier and the objective. The connections between carrier and objective are usually adhesive bonds, which may crack open as a result of the thermal expansions of carrier and objective.